Approximately 93% of motors constructed use iron cores, or variations thereof, to concentrate magnetic flux and boost torque. “Coreless” motors are suited for very high RPM's with low torque and iron core motors usually utilize insulated steel laminations in their stators which reduce heat losses from eddy currents. However, even with thinner laminations, the eddy currents are only blocked in one plane. So to further reduce eddy current losses, silicon is typically added to the steel to reduce its electrical conductivity. Although the silicon reduces some remaining eddy current losses (by reducing the current conductivity), the addition of silicon actually worsens the magnetic conductivity. This reduction of magnetic strength reduces the maximum amount of torque produced, and also reduces electrical efficiency.
Most prior art multi-phase motors use phase windings radially sequenced around the plane of rotation. The close coupled proximity results in “Armature Effect” which reduces efficiency at higher speeds. The usual multi-phase high speed motors also require a gearbox or other loss prone speed reducing device in order to boost torque. Additionally, conventional motors use some variation of axial or radial flux, with multiple salient windings wound around iron type cores. Although this boosts magnetic flux, it also increases inductance and electrical resistance, and reactance. At higher speeds, the inductive and reactive losses limit top speed and efficiency at high speed.
Known prior art direct drive motors include U.S. Pat. No. 4,625,392 issued to Stokes on Dec. 2, 1986 titled Method of manufacturing a molded rotatable assembly for dynamoelectric machines describes molding a rotor of a motor from magnetic material. However, it does not involve Transverse Flux and does not use molded material for the stator.
U.S. Pat. No. 4,853,567 titled Direct Drive Motor issued on Aug. 1, 1989, which describes a three phase outer rotor motor. However, it uses conventional configuration with the three phase windings sequentially located within the same axis, and does not use Transverse Flux.
U.S. Pat. No. 5,777,413 issued to Lange et al. on Jul. 7, 1999 titled Transverse flux motor with magnetic floor gap describes a locomotive motor with Transverse Flux. However, it uses conventional iron laminations as its flux path, and is mainly concerned with physically flattening the motor to allow it to fit into the space between the floor of the locomotive and the train axle.
Prior art transverse Flux motors have historically been too costly to construct, and have rarely been used. This invention simplifies construction and lowers costs of Transverse Flux motors, and at the same time increases electrical efficiency to a higher level than before.
The motor of the present invention overcomes a problem with prior art motors by using separate, independent, uncoupled planes for each phase, and phase and pulse timing to eliminate the “Armature Effect” which results is much higher efficiency at higher speed. The novel motor also has very high torque and can drive directly most loads (such as vehicle tracks, wheels, or propellers) without requiring clutches, gearboxes, or other speed reducing devices. The result is greater efficiency, lower costs, and fewer moving parts.
The present invention also overcomes prior problems associated with boosting magnetic flux, which increases inductance and resistance and at higher speeds, the inductive losses limit top speed and efficiency at high speed. The direct drive motor of the present invention can use radial flux construction, but the preferred embodiment is Transverse Flux construction. In Transverse Flux construction, one large single winding powers each phase. Because magnetic flux is directly proportional to Ampere-Turns, the same magnetic flux can be achieved with more turns with less amperage, or higher amperage and fewer turns. In the preferred embodiment, this novel motor has fewer turns, and higher amperages. With fewer turns, the inductance is less, and with larger copper conductors the electrical resistance is less also. Since the inductance and resistance are reduced, both the inductive losses and the resistive losses are greatly reduced which results in higher efficiency and also a much higher speed usable range.